Fingerprints are tiny and often invisible clues left at a crime scene. They are left because:
Human skin has a slight oiliness due to secretions from glands, perspiration and dead skin.
When people touch something, the ridges on fingers come into contact with the other surface. The oiliness on fingers is transferred on to the object. This is a fingerprint.
How are fingerprints useful in forensic science?
Fingerprints have been a useful tool in forensics for many years. Their value is based on the fact that your fingers and thumbs have a characteristic pattern of ridges and that no two fingerprints are the same. This means:
Your fingerprints are unique to you - they are not the same as the fingerprints of any other person.
Each finger on your hand has a different fingerprint. No two of your fingers are the same.
Identical twins have different fingerprints.
Fingerprints can be classified into groups so they can be stored and matched quickly.
Frequency of the main fingerprint groups
Arch pattern - 5%
Arch 5%
Loop pattern - 65%
Loop 65%
Whorl pattern - 15%
Whorl 15%
Composite pattern - 15%
Composite 15%
Fingerprints are distinctive not only because of their patterns of arches, loops or whorls, but also because of a range of other variations called minutiae. Minutiae are the tiny details that make each print quite distinctive.
Six types of minutiae
More information on the basics of fingerprints can be found at the following websites.
Fingerprints are left on a surface because of perspiration passing through the pores of the fingers. The perspiration is left on the surface as a fingerprint. Depending on the type of surface, one of a number of techniques can be used to collect the fingerprint. Normally fingerprints left at the scene of a crime are invisible (latent) and need to be "dusted" to be seen.
When special powder is brushed on to the prints, small particles of powder cling to the print. The print is then 'lifted off' using sticky-tape. Ordinary household sticky-tape is sometimes used; the picture on the right shows a special sticky sheet with a label for writing on. Steps for collecting fingerprints ||
surface with no visible fingerprints
Step 1: latent prints ||
surface with dark fingerprints showing
Step 2: after powdering ||
gloved hand with fingerprinting tape
Step 3: 'lifting' prints ||
Movie
If you have a fast internet connection, view these movie clips:
Fingerprints taken from a crime scene are compared with the fingerprints of suspects using computer software.
Two fingerprints being compared
See a larger view.
The picture shows two fingerprints being compared on a computer at the Tasmania Police Forensic Laboratory. The faint green markings on the prints are 'points of similarity' placed by the operator with a mouse click.
Police try to find as many fingerprints at a crime scene as possible, with at least 7 matches generally needed to 'prove' the match.
Links
Fingerprint identification By Salil Prabhakar and Anil Jain.
<http://biometrics.cse.msu.edu/fingerprint.html>
Computers are used to store information about fingerprints, as there are now many millions of prints on file in Australia. Computers also scan and automatically classify fingerprints. In Tasmania this has meant that what was once the work of 12 police officers is now the work of a very small team. A central file for fingerprints is stored in Canberra and can match a fingerprint entered from anywhere in Australia within minutes.
Activity
First, visit the website below.
Links
NCIC fingerprint codes By the Brazoria County Sheriff's Department.
<http://brazoria-county.com/sheriff/id/fingerprints/id%7Encic.htm>
Work out the answer to the question below. Share your answer with others and your teacher. A known villain has an NCIC classification of FPC/ 53TTPIAA07DOCM04DI62
What can that classification tell you about the fingerprints on the villain's left hand middle finger and his right hand thumb?
Discuss your answer with others.
Activity
Compare your fingerprints with others
Use an ink pad to take your own fingerprints. Take all ten and mark them to show which is your left hand and right hand. Examine them using the information on this page and the websites listed here. Compare your prints with those of other students. Are there any students whose fingerprints are similar to yours? Test your detective skills
Have one mystery person in your class or group handle a glass and then use coloured chalk dust or fingerprint powder to highlight the prints on it. Without touching the print area on the glass, compare the prints with those of each student. Who is the mystery person? Were you able to decide beyond doubt or could you only narrow it down to a small group of possible suspects? ||
Fingerprints are tiny and often invisible clues left at a crime scene. They are left because:
Fingerprints have been a useful tool in forensics for many years. Their value is based on the fact that your fingers and thumbs have a characteristic pattern of ridges and that no two fingerprints are the same. This means:
- Your fingerprints are unique to you - they are not the same as the fingerprints of any other person.
- Each finger on your hand has a different fingerprint. No two of your fingers are the same.
- Identical twins have different fingerprints.
- Fingerprints can be classified into groups so they can be stored and matched quickly.
Frequency of the main fingerprint groupsArch 5%
Loop 65%
Whorl 15%
Composite 15%
More information on the basics of fingerprints can be found at the following websites.
<http://onin.com/fp/fphistory.html>
<http://www.fingerprints.tk>
<http://brazoria-county.com/sheriff/id/fingerprints/index.htm>
Fingerprints are left on a surface because of perspiration passing through the pores of the fingers. The perspiration is left on the surface as a fingerprint. Depending on the type of surface, one of a number of techniques can be used to collect the fingerprint. Normally fingerprints left at the scene of a crime are invisible (latent) and need to be "dusted" to be seen.
When special powder is brushed on to the prints, small particles of powder cling to the print. The print is then 'lifted off' using sticky-tape. Ordinary household sticky-tape is sometimes used; the picture on the right shows a special sticky sheet with a label for writing on.
Steps for collecting fingerprints ||
Step 1: latent prints ||
Step 2: after powdering ||
Step 3: 'lifting' prints ||
Fingerprints taken from a crime scene are compared with the fingerprints of suspects using computer software.
See a larger view.
The picture shows two fingerprints being compared on a computer at the Tasmania Police Forensic Laboratory. The faint green markings on the prints are 'points of similarity' placed by the operator with a mouse click.
Police try to find as many fingerprints at a crime scene as possible, with at least 7 matches generally needed to 'prove' the match.
Fingerprint identification By Salil Prabhakar and Anil Jain.
<http://biometrics.cse.msu.edu/fingerprint.html>
Computers are used to store information about fingerprints, as there are now many millions of prints on file in Australia. Computers also scan and automatically classify fingerprints. In Tasmania this has meant that what was once the work of 12 police officers is now the work of a very small team. A central file for fingerprints is stored in Canberra and can match a fingerprint entered from anywhere in Australia within minutes.
NCIC fingerprint codes By the Brazoria County Sheriff's Department.
<http://brazoria-county.com/sheriff/id/fingerprints/id%7Encic.htm>
Work out the answer to the question below. Share your answer with others and your teacher.
A known villain has an NCIC classification of FPC/ 53TTPIAA07DOCM04DI62
What can that classification tell you about the fingerprints on the villain's left hand middle finger and his right hand thumb?
Discuss your answer with others.
Compare your fingerprints with others
Use an ink pad to take your own fingerprints. Take all ten and mark them to show which is your left hand and right hand. Examine them using the information on this page and the websites listed here. Compare your prints with those of other students. Are there any students whose fingerprints are similar to yours?
Test your detective skills
Have one mystery person in your class or group handle a glass and then use coloured chalk dust or fingerprint powder to highlight the prints on it. Without touching the print area on the glass, compare the prints with those of each student. Who is the mystery person? Were you able to decide beyond doubt or could you only narrow it down to a small group of possible suspects? ||